In care-giving environments, many elderly and post-surgical patients are at a heightened risk of falling. Because falls increase the risk of additional injury, the patient requires monitoring by a caregiver. Various types of monitoring devices and systems have been developed, the most common type being an electronic monitor.
Electronic monitors sense an initial status of the patient and generate a signal when that status changes, for example, the patient has sat up in bed, left the bed, or risen from a chair. The monitor typically comprises an outer casing containing two electrode plates separated by a spacer. When external pressure is applied to the outer casing, the casing presses downward until the electrode plates make contact with one another through holes in the spacer. The connection indicates the patient is in the bed and causes an alarm to silence.
Although electronic monitors have captured 100% of the patient bed monitor market, the monitors have serious disadvantages. The monitors rely upon electrical leads and opposing conductive surfaces, both of which tend to wear or break in a relatively short time period. Because electrical circuitry is involved, the monitors cannot be used in certain patient environments and the potential for shock exists. Isolation circuits attempt to reduce the risk of shock but cannot eliminate the risk to the point at which Underwriters Laboratories certification may be obtained.
Another disadvantage of electronic monitors is the outer casing cannot be an enclosed envelope. In an enclosed envelope, entrapped air prevents the electrodes from coming into contact with one another. Therefore, an opening must be placed along a seam to allow entrapped air to escape. This opening, however, provides a passageway for contaminants to enter an interior of the monitor, making it unfit for multiple patient use. Moving the opening farther away from the patient—for example, by way of a pneumatic tube connected to the casing—still results in a contagion pathway.
Still yet another disadvantage of an electronic monitor is its stiffness, which contributes to patient discomfort. A certain amount of stiffness is required in the outer casing and the spacer to keep the electrodes from coming into contact with one another absent external pressure. Even if the outer casing is composed of a softer, more flexible material, the spacer still needs to retain its stiffness to keep the electrodes apart.
The disadvantages of electronic monitors have led to attempts to produce pneumatic patient bed monitors. Similar to an electronic monitor, the pneumatic monitor senses an initial status of the patent and generates a signal when that status changes. Although this type of monitor may be used in almost any patient environment, the various designs proposed to date have serious flaws. Because the monitor relies upon an air-filled envelope, it lacks a precise triggering event and is susceptible to high frequency response due to the patient shifting within the bed or chair. Attempts to control high frequency response have involved the use of stiffer casings and pressure plates, all of which significantly decrease patient comfort. Additionally, the monitor is subject to leaks, which trigger false alarms, and therefore must be equipped with an inflation valve. The valve, in turn, becomes another potential failure point. Because of these and other problems, no pneumatic patient bed monitor is manufactured or sold. A need exists, therefore, for an improved pneumatically operated patient bed monitor.